Harass second-grade assembly (6)
I believe the answer is:
badger
'harass' is the definition.
('badger' can be a synonym of 'harass')
'second-grade assembly' is the wordplay.
'second' becomes 'b' (B can mean second eg B-side**).
'assembly' is an anagram indicator.
'grade' with letters rearranged gives 'adger'.
'b'+'adger'='BADGER'
(Other definitions for badger that I've seen before include "Member of the weasel family" , "Grab Ed from the animal" , "One of the weasel family" , "nocturnal creature" , "Pester - nocturnal animal" .)